Patent document U.S. Pat. No. 4,485,069 describes a superheater bundle of this type in which the tubes are disposed inside a cylindrical frame having a circular right cross-section and suspended via dovetail attachments inside an outer frame which is likewise circular and which is connected to the overall structure of the separator-superheater.
In such a bundle, the sloping outermost side rows of tubes in a triangular pitch configuration cannot be occupied in full because the ends of the sloping line segments on which these tubes ought to be located intersect the cylindrical frame and it is not possible to place tubes in the immediate vicinity of the frame. As a result, there are empty spaces round the sides of the bundle, and consequently the steam to be superheated tends to run preferentially therealong because of the lower resistance to steam flow. This gives rise to the steam being heated unevenly, and in addition, the number of tubes in the bundle is not optimum for the cross-sectional area occupied by the bundle.
U.S. Pat. No. 3,326,280 describes a horizontal heat exchanger for reheating and vaporizing a fluid flowing around a bundle of tubes along which there flows a gas which is subjected to cooling and condensation, said tubes being disposed in a rectangular pitch within a frame which is polygonal in shape.
In such a heat exchanger, the number of tubes in the bundle is relatively limited and consequently so is the heat exchange area per unit of cross-section.
The object of the present invention is to provide a superheater bundle for a horizontal steam separator-superheater which fills the right cross-section of its frame uniformly, with the number of tubes per unit right cross-section being optimum, and avoiding any tendency of the steam to be superheated flowing preferentially along the frame.